TechSpot

Dell 4700 will not power up

By banobo
Sep 22, 2009
  1. Is there a way to "jump start" the computer? I am not sure if I am dealing with a dead motherboard or a simple bad power button assembly.

    I have a Dell Dimension 4700. I powered it off normally, but now it will not power on. It did this once before, but a few hours later it started normally. This time it will not start. The power led and diagnotic leds do not light at all. The PSU seems okay. I was able to disconnect and jump the the 20-pin connector from the PSU to the mboard and start the PSU fan, and the "flea" light is on whenever the power cable is connected, however, the power led never comes on.

    I have gone so far as to remove everything attached to the mboard (including RAM, etc.) except the PSU but I still get nothing.

    Any suggestions would be greatly appreciated.
     
  2. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    Replace the power supply
     
  3. raybay

    raybay TS Evangelist Posts: 10,716   +6

    I second TMagic650. You need a power supply tester to tell if the power supply is bad or good. If it seems good, but is not working, it is bad. Replace it or at least trade out temporarily with another power supply to test.
    The Dimension 4700 is an excellent computer that does not often break down, but the power supply is barely adequate... If you had added components that draw more power, they will somtimes wipe out once channel of the power supply, while the other two are good, or appear to be good.
    You do have to be careful in buying a replacement, because many power supply power switches and air flow gates are not designed the same way as most power supplies. You do need to have one which has the power switch in the same location as the Dell power supply.
     
  4. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    "but the power supply is barely adequate"...

    That's what I have seen, and I have replaced a bunch of these supplies
     
  5. banobo

    banobo TS Rookie Topic Starter

    Thanks for the responses...this is a great chat board.

    I replaced the power supply, a lot easier than replacing a motherboard, but it made no diference at all. Can someone tell me if what I bought may not be compatible? Raybay mentions to be careful. The original power supply is a 305-watt, but it does not have an external power switch. The only changes I made to the 4700 was a slightly uprgaded video card (PCI express instead of integrated) and maxed out the RAM.

    I bought a Dynex 400-watt ATX12V V2.2.

    Thanks!
     
  6. raybay

    raybay TS Evangelist Posts: 10,716   +6

    That should have worked... double check all your plugs and sockets...

    That machine will refuse to start if the CMOS battery is bad, or if the CPU cooling fan is not working... perhaps others. Or if memory modules have gone bad.

    Look carefully at your motherboard for those little barrel-like devices poking up... they are about 1 1/4 to 1 1/2 high... Do any look puffy? Do any have black or bronze colored powder leaking from them?

    Did your computer quit suddenly... while on... or did it just refuse to start some morning?

    Remove one memory module and try a boot.
    Then
    Change, put that module back, and remove the other module.

    There is a small enclosure in which you can see a shiny device about the size or a US Quarter coin, but more than twice as thick... you might borrow one of these cmos batteries from another computer, or buy one at Wal-Mar or Best-Buy for $3.50 to $4.50, or perhaps $60 at Radio Shack (just kidding)
    Replace that battery, either buy borrowing or buying one.

    Do any lights come on anywhere on the board or case?

    Have you checked your power socket where you live to be sure your circuit breaker has not popped open?

    Triple check the installation of cables for the power supply to be sure you don't have one plugged into the wrong spot... or have left one unplugged altogether.

    Be sure your existing case switch is not locked open...
     
  7. banobo

    banobo TS Rookie Topic Starter

    Thanks Raybay.

    I will try the battery and the fan as soon as possible. If either of these were "bad" shouldn't I still get something? As it is, I get nothing...no power indicator lights up or diagnostic lights, harddrives don't spin up...nothing.

    Nothing burst, buldging or leaking.

    It did not quit suddenly. I shut it down one day, normally, and it would not start, was completely dead. A few hours later, it boot normally. After a few weeks, I shut it down and this time it has stayed dead.

    I have removed all the RAM, etc., it made no diference.

    The only light that comes on is the "flea" light, the little green light on the motherboard, nothing else.

    I have confirmed, and yes, triple checked, all power outlets, connections, etc. :)

    I am not sure what you mean by the case switch being locked open...for convienience, I have it disconnected from the front panel.
     
  8. raybay

    raybay TS Evangelist Posts: 10,716   +6

    Somehow it seams more like a power switch than a power supply... or a cpu fan... something that makes the computer go into a protective shutdown mode.

    I am going to get a 4700 out of the shop and refamiliarize myself with what things go wrong... What you tell us is odd for a 4700... even though it is nearing four years old?
    What you describe is rather atypical for that model.

    Hard drive known good?
    Any electrical burn smells.
    Any oily looking colors anywhere on the motherboard.
     
  9. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    I would go for the motherboard now. The capacitor check may or may not show bulging or leaking caps. Case power switches do go bad very, very rarely
     
  10. banobo

    banobo TS Rookie Topic Starter

    Okay...so I don't have a fan that I can swap out (I do have an 8110, but it has a diferent connector). I was able to grab the battery out of it though, but still nothing.

    If the fan had gone bad, I would still get a power indicator light and most likely it would at least boot to a point, right? Same with RAM or a bad card. If the board was good, wouldn't I at least get something rather than nothing?

    I have never had a mother board go out, so I don't know what it looks like, but I had every other thing happen...video card, ram, drives, etc.

    No oily colors or anything. The mother board even looks reasonably clean.

    Soooo...I took the switch out of the 8110, and forgot to turn off the power supply, etc. When i started to plug it in, I got a power indicator light for a second, but that was all. Everything is still dead.

    Soooo...motherboard?
     
  11. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    "Soooo...motherboard?"...
    It just about has to be the motherboard. I think any quality miniATX motherboard with 2 or 3 PCI slots would fit. It would be a good time to upgrade the CPU and memory. Is this an Intel Celeron motherboard?
     
     
  12. banobo

    banobo TS Rookie Topic Starter

    I think you're right. Its a pentium (775 socket).
     
  13. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    It's a newer model than I am used to working on, but I know that the bios on the original board was very limited. If it had 3 PCI sockets, go with 3 on the new board. Does it have DDR or DDR2 memory?
     
  14. banobo

    banobo TS Rookie Topic Starter

    okay...so I got a new motherboard and processor. Everything seems fine till I get the to the windows splash screen and then it re-boots...what did I miss?
     
  15. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,929   +167

    You are quick! Did you format and install Windows fresh. You will have to do this, did you forget?
     
  16. banobo

    banobo TS Rookie Topic Starter

    Shoot...did not think of that. Impatience. Thanks!
     
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